The wiring harness along the those plugs have long been discontinued by GM.
There is no aftermarket.
I had a former member make me a wiring harness for mine to work with a factory switch. He had no luck finding the mate for that plug either.
When he made the harness, he used a different style plug & sent along the mate with so I could modify the wiring at the light.
Like I said...'former member'. (That's a story unto itself) But, there are a few current members here that are making 4-Hi wiring kits along with a few other wiring harnesses. I'm sure that they have the tech to be able to make one up for you. It's a fairly common need, so that may be another market for them.
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